I have a humming noise in the drivetrain. It is constant as long as the car is rolling and changes pitch with the cars speed. Worse around 50-55 mph. I am sure it's in the drivetrain and not the engine. Both half shaft assemblies were changed recently (160K miles) due to leaking boots. hard to tell exactly where noise is comming from. Sounds more centered but could be comming from the passenger side. I am hoping it's a bad hub bearing, (easy fix) but wonder if it could be in the transaxle $$$$$. Any thoughts are appreciated.